'use strict';

const fs = require('fs');
const path = require('path');
const paths = require('./paths');
const chalk = require('react-dev-utils/chalk');
const resolve = require('resolve');

/**
 * Get additional module paths based on the baseUrl of a compilerOptions object.
 *
 * @param {Object} options
 */
function getAdditionalModulePaths(options = {}) {
	const baseUrl = options.baseUrl;

	// We need to explicitly check for null and undefined (and not a falsy value) because
	// TypeScript treats an empty string as `.`.
	if (baseUrl == null) {
		// If there's no baseUrl set we respect NODE_PATH
		// Note that NODE_PATH is deprecated and will be removed
		// in the next major release of create-react-app.

		const nodePath = process.env.NODE_PATH || '';
		return nodePath.split(path.delimiter).filter(Boolean);
	}

	const baseUrlResolved = path.resolve(paths.appPath, baseUrl);

	// We don't need to do anything if `baseUrl` is set to `node_modules`. This is
	// the default behavior.
	if (path.relative(paths.appNodeModules, baseUrlResolved) === '') {
		return null;
	}

	// Allow the user set the `baseUrl` to `appSrc`.
	if (path.relative(paths.appSrc, baseUrlResolved) === '') {
		return [paths.appSrc];
	}

	// If the path is equal to the root directory we ignore it here.
	// We don't want to allow importing from the root directly as source files are
	// not transpiled outside of `src`. We do allow importing them with the
	// absolute path (e.g. `src/Components/Button.js`) but we set that up with
	// an alias.
	if (path.relative(paths.appPath, baseUrlResolved) === '') {
		return null;
	}

	// Otherwise, throw an error.
	throw new Error(
		chalk.red.bold(
			'Your project\'s `baseUrl` can only be set to `src` or `node_modules`.' +
        ' Create React App does not support other values at this time.'
		)
	);
}

/**
 * Get webpack aliases based on the baseUrl of a compilerOptions object.
 *
 * @param {*} options
 */
function getWebpackAliases(options = {}) {
	const baseUrl = options.baseUrl;

	if (!baseUrl) {
		return {};
	}

	const baseUrlResolved = path.resolve(paths.appPath, baseUrl);

	if (path.relative(paths.appPath, baseUrlResolved) === '') {
		return {
			src: paths.appSrc,
		};
	}
}

/**
 * Get jest aliases based on the baseUrl of a compilerOptions object.
 *
 * @param {*} options
 */
function getJestAliases(options = {}) {
	const baseUrl = options.baseUrl;

	if (!baseUrl) {
		return {};
	}

	const baseUrlResolved = path.resolve(paths.appPath, baseUrl);

	if (path.relative(paths.appPath, baseUrlResolved) === '') {
		return {
			'^src/(.*)$': '<rootDir>/src/$1',
		};
	}
}

function getModules() {
	// Check if TypeScript is setup
	const hasTsConfig = fs.existsSync(paths.appTsConfig);
	const hasJsConfig = fs.existsSync(paths.appJsConfig);

	if (hasTsConfig && hasJsConfig) {
		throw new Error(
			'You have both a tsconfig.json and a jsconfig.json. If you are using TypeScript please remove your jsconfig.json file.'
		);
	}

	let config;

	// If there's a tsconfig.json we assume it's a
	// TypeScript project and set up the config
	// based on tsconfig.json
	if (hasTsConfig) {
		const ts = require(resolve.sync('typescript', {
			basedir: paths.appNodeModules,
		}));
		config = ts.readConfigFile(paths.appTsConfig, ts.sys.readFile).config;
		// Otherwise we'll check if there is jsconfig.json
		// for non TS projects.
	} else if (hasJsConfig) {
		config = require(paths.appJsConfig);
	}

	config = config || {};
	const options = config.compilerOptions || {};

	const additionalModulePaths = getAdditionalModulePaths(options);

	return {
		additionalModulePaths: additionalModulePaths,
		webpackAliases: getWebpackAliases(options),
		jestAliases: getJestAliases(options),
		hasTsConfig,
	};
}

module.exports = getModules();
